Background on Genetic Causes of Infertility in Males

Chromosomes are microscopic structures which contain the genetic material used to construct and maintain the body. They can be though of as a combination of blueprints and instruction manual. Genes contain basic instructions which direct the cells in the body. Just as missing parts of a blueprint or instructions for a house might mean that the kitchen does not get build or the dishwasher does not work properly, genetic conditions can result in malfunction of the body. A wide variety of genetic abnormalities can result in problems with fertility.

Humans normally have 46 chromosomes. There are 22 types of somatic chromosome of which 2 copies exist (for a total of 44) and 1 pair of sex chromosomes (for a total of 2). The sex chromosomes in males are an X chromosome and a Y chromosome (XY), whereas females have 2 X chromosomes (XX). Males are genetically described as 46 XY and females as 46 XX.

The causes of infertility can be categorized in a number of ways:

Genetic vs. Non-genetic

Reversible vs. Irreversible

Treatable or non-treatable

Whlle genetic conditions are not 'reversible' with current technology, identifying a genetic condition is critical in infertile males because:

A genetic cause may be transmitted to offspring.

Identifying the specific genetic cause can provide important information on the chances that sperm production is present in the testis even if there are no sperm in the ejaculate.

Some genetic diseases are associated with health problems in addition to infertility. Preventing those problems is important.

Which men with infertility should be evaluated for genetic causes?

Genetic abnormalities are very uncommon in men with sperm concentrations >5 million/ml - in fact, the chances of a genetic abnormality if the sperm count is > 5 million/ml is the same as in the general population.

Testing for genetic abnormalities is useful only if there are < 5 million sperm per ml.

What are the genetic abnormalities that can be present?

Despite the large number of genetic abnormalities associated with infertility, there are 4 major types of genetic problems which constitute the bulk of diagnoses.

With increasing genetic testing, Y-chromosome microdeletion is increasingly recognized as the most common identifiable cause of non-obstructive azospermia.

How are Genetic Abnormalities Diagnosed?

While there may be clinical features that suggest one cause or another, a precise diagnosis requires genetic testing. All genetic tests are done with a blood sample. A sperm is a complex DNA transport vehicle and virtually all of the chromosomes are involved in sperm production. Note that there are many genetic causes that are currently unknown and that cannot be tested for at this time. The frequently used genetic tests used in infertile men are:

Karyotype: determines the number and type of chromosomes. Large defects in chromosoms can sometimes be tested, but specific genes are not identified. Analogous to checking that all of the volumes of an encyclopedia are present and that the order of the books is correct.

Y-chromosome microdeletion: checks the distal arm of the Y-chromosome which is important in sperm production. See more below

Cystic fibrosis testing: checks for the absence or presence of genes commonly involved in cystic fibrosis and absence of the vas deferens.

It is important to recognize that virtually every genetic abnormality will have a spectrum of severity in terms of clinical presentation. Quite frequently, men who are diagnosed later in life as a result of infertility fall into the milder range of the disease.

Klinefelter's syndrome (KS) results from the presence of an extra X chromosome in a male. The karyotype in KS is 47 XXY. Under normal circumstances during sperm or egg production, the 46 chromosomes of an individual are divided into two groups of 23 chromosomes. Each egg or sperm contains 23 chromosomes. Once the egg and sperm combine to form an embryo, there are once again 46 total chromosomes, with half coming from the father and half from the mother.

The sex chromosomes (the X and Y chromosome) normally divide before an egg or sperm is made such that the woman will contribute one of her two sex chromosomes and the man will contribute one as well. Because a woman has 2 X chromosomes, she can only contribute an X to the egg; because males have and X and a Y chromosome, men can contribute either an X or a Y to the sperm. Occasionally, during division of the sex chromosomes either the XX or XY pair will fail to separate (non-disjunction) and the male or female will contribute 2 sex chromosomes instead of 1. The end result is that the offspring will have an extra sex chromosome - 3 instead of the normal 2; one result of having an extra sex chromosome is the 47 XXY karyotype.

Klinefelter's syndrome is much more common that was previously appreciated. KS affects about 1 in 500 men. In the past, only the most severely affected individuals were identified since they often presented with manifestations of KS other than just infertility. Today, very mild forms of KS can be detected with genetic testing, which is often done for infertility, and whould not have been recognized otherwise because the individuals appear perfectly normal. It is important to recognize this because most men with Klinefelter's will not have the types of problems described in the historical literature - such as mental retardation, low testosterone or poor virilization. The fallicies regarding the clinical symptoms of KS may be propegated on the internet. In reality, there is a wide spectrum of clinical features in Klinefelter's syndrome and most men with KS live perfectly normal lives - with the excpetion of reproduction. Many men with KS will have normal intelligence, advanced degress, appear completely normal and not have any of the behavioral problems which are sometimes mentioned in text books. Therefore, take care when reading about KS on the internet because the information may be outdated.

DIAGNOSIS

Ultimately, the diagnosis of Klinefelter's disease is done with genetic testing of the blood - a karyotype. The common features that are suggestive but not definitive include small testes, a specific pear-shaped body habitus and gynecomastia. Lab testing will usually demonstrate a high follicle stimulating hormone and leutenizing hormone with low testosterone. A low testosterone is not seen in all men with KS, and some may have 'higher than normal' levels of testosterone.

TREATMENT

Microdissection of the testis (microTESE) has demonstrated the presence of sperm in about 50% of men with Klinefelter's syndrome. Any sperm harvested in this manner require IVF+ICSI for fertilization. Genetic counseling is required in all men prior to consideration of IVF because there is a small risk of transmission to the offspring. Based on the limited success of the frozen/thawed approach, the use of fresh sperm with a coordinated IVF-ICSI cycle is recommended.

There are additional issues pertaining to men with Klinefelter's syndrome including an increased risk of breast cancer, osteoporosis and other rare tumors. Men often require life long testosterone supplementation.

Long-Term Management

Issue

Comments

HORMONES

Puberty and secondary sexual characteristics (e.g. beard) may be delayed.

Increased breast tissue is common - 50-75% of males will have this.

Testosterone supplementation is frequently utilized, but reproductive goals need to be clarified before administration. It is possible to raise testosterone levels without taking testosterone.

Reduced thyroid function (hypothyroidism) is uncommon, but can occur. Thyroid inflammation is common.

Thyroid stimilating hormone and T4 levels should be measured yearly.

TUMORS

Men with Klinefelter's are at increase risk for germ cell tumors and breast cancer.

Germ cell tumors: those tumors involving cells capable of developing into any tissue - such as those found in the testis, but also the retroperitoneum or mediastinum. Very uncommon and there are no standard recommendation for screening tests.

Breast cancer: the risk is markedly elevated compared to other men (20-50x), but the overall incidence is still lower than for women. Periodic self exam and yearly breast exam by a doctor should be undertaken.

IMMUNE DISEASES

Diabetes is more common as are some autoimmune disorders. The exact amount of increased risk is unclear.

Yearly fasting glucose is recommended.

On the Web

The Y-chromosome contains critical instructions for the production of sperm. If segments of the Y chromosome are missing, then sperm production is usually impaired. The size/length of the deletion and its location are important in determining if sperm production could be present in the testis, even if there are none in the ejaculate. Short deletions limited to the distal end (towards the tip) of the long arm of the Y-chromosome are associated with a very high probability of spermatogenesis being present. Conversely, extensive or proximal defects (towards the center) are usually associated with the complete absence of sperm production. Determing the location and length of the deletion are very important in determining the utility of looking for sperm in the testis.

Y-Chromosome: one of 46 chromosomes in the body. The long arm contains genes involved in sperm production. The AZFa, AZFb and AZFc are geographic areas that contain genes, but are not names of genes. These areas actually overlap. AZFa is at the 'proximal end' and AZFc at the 'distal end' of the long arm. The terminology is variable, but the basic concept is that there is missing genetic material from different areas of the Y-chromosome and in varying amounts which affects sperm production.

DIAGNOSIS

A specific genetic test from a blood sample is required. The primary difference between testing methods is based on the number of areas that are tested with anywhere from 6 to 24 areas being checked. There is limited value in testing more than 6-8 areas of the long-arm of the Y-chromosome. Hormone testing usually demonstrates an elevated FSH in the teens (normal being less than about 6) and modestly elevated LH; the testosterone is normal to low-normal. Testis size is usually diminished.

TREATMENT

There are no known health repercussions from Y chromosome microdeletions except for infertility. It can be transmitted to male offspring. Depending on the chances that sperm will be found in the testis, a decision can be made if a microTESE is warranted. Note that some men with very mild (short and distal) Y-MD may have sperm in their ejaculate. Any sperm retrieved from males with Y-MD require IVF and ICSI to achieve a pregnancy.

Probability of sperm retrieval with micro TESE in azospermic males

Region(s)

Percent of Y-MD

Probability of Successful

Sperm Retrieval

AZFc (b2/b4)

65%

50%

AZFb-c

15%

<5%

AZFa

10%

15-75% (0% if complete)

AZFb

10%

60%

AZFa-b-c

2%

0%

Note that male offspring will receive the defective Y-chromosome and be affected by infertility as adults. Some males with YMD have sperm production early in life which is lost later on. Therefore, if a couple chooses to use sperm with YMD and has a male offspring, it may be worthwhile to have their son's semen analysis checked early in puberty and to cryopreserve sperm if any are found. Options to avoid transmission include primplantation genetic diagnosis and the transfer of female embryos only, or the use of donor sperm.

IMPORTANT NOTICE REGARDING Y-CHROMOSOME MICRODELETION TESTING

Y-MD testing is a very important test in the evaluation of males with infertility, most importantly in those with non-obstructive azospermia (as detailed above). Despite this importance, the BC Medical Services Plan has declined to provide this test as an insured service. As of April 8, 2013 the costs have been passed along to patients (including those with MSP coverage). Dr. Sai Ma is offering the test free of charge for those patients who agree to

Process for obtaining Y-MD testing through VGH - approx $350.

Pre-payment must occur before the sample will be collected or testing initiated for Y-MD testing

Cystic fibrosis (CF) is an autosomal recessive condition which is common in individuals of Northern European ancestry. This means that abnormalities in both copies of the genes responsible for CF are required. Carriers (individuals with abnormalities in only one copy) do not have any clinical symptoms nor do they have any problems with fertility. Approximately 1 in 25 individuals of Northern European decent are carriers.

If the vas deferens is obstructed, sperm are blocked from passing into the ejaculate. This results in sterility. The most common cause of vasal obstruction is surgical - namely vasectomy. Some men, however, are born with obstruction of the vas deferens secondary to a genetic problem. There are 2 general types of gentic abnormalities which can occur:

CFTR gene related problem

Non-CFTR gene related problem - rare accounting for less than 10% of men with an absent vas deferens

The CFTR gene is responsible for secretions in the body. Problems with the CFTR gene result in cystic fibrosis (CF) - a condition in which secretions are thick. Thick secretions result in problems in the respiratory (lungs) and gastrointestinal tracts (pancreas, bowels), but can also affect other organs. Men with CF are born with normal reproductive tracts, but obstruction of the vas deferens and seminal vesicles by thick secretions eventually leads to scarring, atrophy and obstruction. On exam, the vas deferens is not palpable - or if it is, it is usually a thin, firm cord of tissue. Men with CF frequently have problems with infertility because sperm are blocked from making their way from the testis to the ejaculate. Men with CF-associated CAVD present with CF, typically at a young age because of respiratory or other problems. Some men with a very mild form of CF present in adult life with infertility and none of the other symptoms which can be present with CF. In men presenting with this mild form of CFTR gene problem, there are no known long term health risks aside from reproductive ones. Occasionally, a patient with CBAVD may recall frequent episodes of bronchitis or sinusitis.

Other men have genetic abnormalities which do not affect the CFTR gene, but are missing the vas deferens. They may share some aspects of the genetic abnormalities seen with CF, but only have infertility. They do NOT have any of the other problems associated with CF, but there can be problems with development of the kidneys.

DIAGNOSIS

The diagnosis of absence of the vas deferens is as simple as a physical examination and a semen analysis. The presence of a palpable vas deferens and intact epididymis effectively excludes the presence of CBAVD and genetic testing is not necessary. Men with CBAVD will have low-volume, acidic ejaculate without sperm. Hormone parameters are usually completely normal. Determining the underlying genetic cause, however, requires genetic testing on a blood sample. There are a very large number of genes which may result in CAVD or CF, but the majority are on chromosome 7. While genetic testing cannot currently assess all of the possible abnormalities, about 90% can be detected.

Most men with full blown CF have already had genetic testing. Men presenting later in life with CAVD require genetic testing to confirm the diagnosis. In non-CFTR related CAVD, an ultrasound of the kidneys is performed as it can be associated with absence of a kidney - this is not necessary if a CFTR-related defect is confirmed.

The most common genetic mutations associated with CBAVD are those of the F508 deletion and/or 5T mutation. Note that the 5T mutation is not seen in those patients will the full-blown cystic fibrosis (i.e. any clinical symptoms in addition to azospermia).

TREATMENT

Virtually all men with CAVD (both those with CF and those without), have perfectly normal sperm production even though they are blocked from making their way to the ejaculate. Sperm can typically be retrieved either through a PESA/MESA or a TESE. Sperm obtained by these methods require IVF+ICSI.

It is recommened that the partners of men with CAVD be tested for CF carrier status. As mentioned previously, about 1 in 25 people of northern European descent will be carriers. If the partner is a carrier, there is an increased risk of the offspring having cystic fibrosis. If a man has CF and their partner is a carrier, then the risk that their offspring will have CF is 50%. If a man is only a carrier and their partner is a carrier, the risk that their offspring will have CF is 25%.

Consideration should be given to screening the family, especially male siblings, for carrier status.

Because there are many chromosomes and genes involved in sperm production, there are a very large number of potential genetic causes for infertility in a man. We are not currently able to test for all causes, though this will likely be possible in the future. In addition to the 3 most common types of genetic abnormalities responsible for infertility, there are many less common types. The main importance of identifying these conditions is that pre-implantation genetic testing may be indicated to reduce the risk of transmission to offspring. In addition, some types of genetic abnormalities can preclude the presence of spermatogenesis and therefore save a man the cost and complications of undergoing a futile attempt at sperm retrieval.

Other types of genetic abnormalities include:

Aneuploidy: this is an issue with the number of chromosomes. The normal complement in a male is 46 chromosomes, 2 of which are sex chromosomes (X and Y). Examples: Klinefelter's is an example of aneuploidy involving an extra X chromosome - 47 XXY. Down Syndrome have an extra copy of chromosome 21.

Deletions: portion of a chromosome is missing.

Inversions: portion of a chromosome is broken off, turned upside down and reattached.

Translocations: when a segment of one chromosome is transferred to another chromosome. Sometimes information from one chromosome is 'swapped' with information for another. As long as all the information is there, the individual does not usually have a problem. If offspring can be conceived, they may have major congenital defects because they do not have a full 'instruction set'.

Genetic Counseling

The approach to managing males with genetic problems causing infertility, the entire family including the partner and the potential offspring must be considered. Implications regarding transmission of genes to the offspring and the long-term implications is important. The ultimate goal is a healthy, happy family. Genetic counseling is recommended for all individuals. The fertility labs may offer genetic counseling as does the Provincial Medical Genetics Program. Unfortunately, it can take a long time to obtain an appointment at BC Women's Hospital.